The present invention relates to sealing and packaging of microelectromechanical fabricated devices on a device substrate before dicing.
Microelectromechanical systems (MEMS) are miniaturized devices, such as microswitches that may range in size from about 1 micron to about 1 mm. These devices generally require a controlled environment to operate for a long period of time. Introduction of contaminants such as moisture, particulates or oxygen into the gas surrounding the device can cause sticking, contamination, or interference of the metal contacts, leading to device failure. MEMS devices are often manufactured in an array on a silicon wafer, and then separated or diced into individual units. Such separation is called “singulating”. Dicing produces random particles that can contaminate and disable some of the microdevices.
There are known wafer-level packaging processes that may use bonding techniques such as a silicon/gold eutectic bond or gold/gold thermal compression bonding. However, these bonding materials produce an electrically conductive bond, which may introduce constraints as to how the wafers can be bonded and how the device layout may be configured. Another known bonding material is glass frit, or powdered glass. However, this must be screen-printed onto one of the wafers, which can cause contamination of MEMS devices, it limits the process capability of through-wafer cavities and has the potential for outgassing over the operational lifetime of the device.